Enneads III.7: Of Time and Eternity
Plato Does Make Some Statements That Allow of Being Justified
Plato himself, indeed, does say, not that the nature of time is to be a measure or something measured, but that to make it known there is, in the circular movement of the universe, a very short element (the interval of a day), whose object is to demonstrate the smallest portion of time, through which we are enabled to discover the nature and quantity of time. In order to indicate to us its nature ("being"), (Plato[438]) says that it was born with the heavens, and that it is the mobile image of eternity. Time is mobile because it has no more permanence than the life of the universal Soul, because it passes on and flows away therewith; it is born with the heavens, because it is one and the same life that simultaneously produces the heavens and time. If, granting its possibility, the life of the Soul were reduced to the unity (of the Intelligence), there would be an immediate cessation of time, which exists only in this life, and the heavens, which exist only through this life.
TIME AS THE PRIOR AND POSTERIOR OF THE MOVEMENT OF THIS LIFE WOULD BE ABSURD.
The theory that time is the priority and posteriority of this (earthly) movement, and of this inferior life, is ridiculous in that it would imply on one hand that (the priority and posteriority of this sense-life) are something; and on the other, refusing to recognize as something real a truer movement, which includes both priority and posteriority. It would, indeed, amount to attributing to an inanimate movement the privilege of containing within itself priority with posteriority, that is, time; while refusing it to the movement (of the Soul), whose movement of the universal Sphere is no more than an image. Still it is from the movement (of the Soul) that originally emanated priority and posteriority, because this movement is efficient by itself. By producing all its actualizations it begets succession, and, at the same time that it begets succession, it produces the passing from one actualization to another.